Irrigated ablation electrode assembly having off-center irrigation passageway

ABSTRACT

An irrigated ablation catheter includes a shaft and an electrode assembly affixed to a distal end of the shaft. The distal electrode assembly includes a manifold and an ablation electrode affixed together and extending along a center axis. The electrode has a distal irrigation passageway extending therethrough to an opening at a distal tip of the electrode. The opening of the irrigation passageway is offset in distance from the center axis, and allows a thermal sensor such as a thermocouple to be located in a sensor cavity in the electrode on or near the center axis. One variation involves providing a pair of distal irrigation passageways through the electrode where both of the openings of the passageways are offset from the center axis. The thermal sensor in this variation is located in the sensor cavity substantially on the center axis.

BACKGROUND OF THE INVENTION a. Field of the Invention

The present invention relates generally to irrigated ablation catheters,and more particularly, to electrode assemblies having one or more distalirrigation passageways that are off-center.

b. Background Art

Electrophysiology (EP) catheters have been used for an ever-growingnumber of procedures. For example, catheters have been used fordiagnostic, therapeutic, mapping and ablative procedures, to name just afew examples. Typically, a catheter is manipulated through the patient'svasculature and to the intended site, for example, a site within thepatient's heart, and carries one or more electrodes, which may be usedfor mapping, ablation, diagnosis, or other treatments.

There are a number of methods used for ablation of desired areas,including, for example, radio frequency (RF) ablation. RF ablation isaccomplished by transmission of radio frequency energy to a desiredtarget area through an electrode assembly to ablate tissue at the targetsite. Because RF ablation may generate significant heat, which if notcontrolled can result in undesired or excessive tissue damage, such assteam pop, tissue charring, and the like, it is commonly desirable toinclude a mechanism to irrigate the target area and the device withbiocompatible fluids, such as a saline solution. The use of irrigatedablation catheters can also prevent the formation of soft thrombusand/or blood coagulation.

Typically, there are two general classes of irrigated electrodecatheters, i.e., open irrigation catheters and closed irrigationcatheters. Closed ablation catheters usually circulate a cooling fluidwithin the inner cavity of the electrode. Open ablation catheterstypically deliver the cooling fluid through open outlets or openings onor about an outer surface of the electrode. Open ablation cathetersoften use the inner cavity of the electrode, or distal member, as amanifold to distribute saline solution, or other irrigation fluids, toone or more passageways that lead to openings/outlets provided on thesurface of the electrode. The saline thus flows directly through theoutlets of the passageways onto or about the distal electrode member.This direct flow of fluid through the electrode tip lowers thetemperature of the tip during operation, rendering accurate monitoringand control of the ablative process more difficult.

Another known mechanism to control heat is to provide an ablationgenerator with certain feedback features, such as a temperature readoutof the electrode temperature. To provide for such feedback to thephysician/clinician during the procedure, conventional RF ablationgenerators are typically configured for connection to a temperaturesensor, such as a thermocouple, located within the electrode.

A common conventional irrigated ablation catheter design involves theuse of a distal irrigation passageway in combination with anelectrode-disposed thermal sensor. The distal irrigation passageway isthermally insulated and is typically located on the center axis of theelectrode assembly. Because the distal irrigation passageway is locatedon the center axis, the thermal sensor must be moved away from thecenter axial position. This off-center positioning of the thermal sensoris less than ideal since it could affect the temperature measurement.For example, consider the situation where the catheter electrode is in aparallel contact orientation. The temperature reading will depend onwhich side of the electrode is contacting the tissue, since it is on thecontact side of the electrode where the significant heat will begenerated. The preferred location for the thermal sensor would be on ornear the center axis of the electrode.

There is therefore a need to minimize or eliminate one or more of theproblems set forth above.

BRIEF SUMMARY OF THE INVENTION

One advantage of the present invention is that is provides an irrigatedablation electrode assembly with an improved and more consistenttemperature monitoring capability over a broad range of expectedoperating orientations. Another advantage of the present invention isthat it provides such improved temperature monitoring with nosignificant impairment to the distal tip irrigation capability.

The present invention is directed to a distal electrode assembly of anirrigated ablation catheter, where the assembly includes a manifold andan ablation electrode, which together extend along a main or centeraxis. The manifold is configured for connection to a distal end of ashaft portion of the catheter. The ablation electrode has a firstirrigation passageway having a first opening at a distal tip thereof.The first opening is offset in distance from the center axis. Moving thedistal irrigation passageway vacates space in the center of theelectrode, on or near the center axis. Through the foregoing, a thermalor temperature sensor, such as a thermocouple, thermistor or the like,may be disposed within a sensor cavity in the electrode at or near thecenter axis which overcomes the problems described above.

In one embodiment, the irrigation passageway is thermally insulated,such as through insertion of a thermally insulated tubular element. Inanother embodiment, the distal assembly includes first and secondirrigation passageways with respective first and second openings at thedistal tip of the electrode to define a dual distal irrigationpassageway ablation electrode assembly. These dual irrigationpassageways have respective openings that are both offset in distancefrom the center axis so as to allow the temperature sensor to be placedat or near the center axis, thereby improving temperature monitoringperformance.

A catheter including the inventive electrode assembly and a method ofmanufacturing an irrigated ablation catheter are also presented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of an exemplary RF ablation environment inwhich embodiments of the invention may be used.

FIG. 2 is a cross-sectional view of an irrigated ablation electrodeassembly having a conventional configuration.

FIG. 3A is a cross-sectional view of a first embodiment of an electrodeassembly having a distal irrigation passageway through an ablationelectrode, and which has an opening that is offset in distance from acenter axis.

FIG. 3B is a front view of the electrode assembly of FIG. 3A, moreclearly showing the distal opening of the off-center irrigationpassageway.

FIG. 4A is a cross-sectional view of a second embodiment of an electrodeassembly of the present invention, having dual, straight irrigationpassageways having respective openings both of which are offset indistance from the center axis.

FIG. 4B is a front view of the electrode assembly of FIG. 4A.

FIG. 5A is a cross-sectional view of a third embodiment of an electrodeassembly of the present invention, with dual off-center irrigationpassageways having straight and curved sections.

FIG. 5B is a front view of the electrode assembly of FIG. 5A.

FIG. 6 is a perspective view showing the distal electrode assembly ofFIG. 5A.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein like reference numerals are usedto identify identical components in the various views, FIG. 1 is asimplified, perspective view of a system 10 for conducting a diagnosticor therapeutic function, which in the illustrated embodiment shows an RFablation configuration. The system 10 includes an irrigated ablationcatheter 12 operably connected to a fluid source 14, such as a pumpassembly, and an energy source, such as an RF ablation generator 16.FIG. 1 generally illustrates an irrigated ablation catheter 12 of thetype that may be provided by and/or used in connection with the presentinvention. The remainder of the system 10 may comprise conventionalcomponents. In this regard, the fluid source 14 and the RF ablationgenerator 16 may serve to facilitate the operation of an ablationprocedure and may involve monitoring any number of chosen variables(e.g., temperature of the ablation electrode, ablation energy) andproviding the requisite energy source. Furthermore, additionalcomponents may be integrated into the system 10, such as visualization,mapping and navigation components known in the art, including amongothers, for example, an EnSite NavX™ system 15 commercially availablefrom St. Jude Medical, Inc., and as also seen generally by reference toU.S. Pat. No. 7,263,397 entitled “METHOD AND APPARATUS FOR CATHETERNAVIGATION AND LOCATION AND MAPPING IN THE HEART” to Hauck et al., ownedby the common assignee of the present invention, and hereby incorporatedby reference in its entirety. Additionally, an electrophysiological (EP)monitor or display such as an electrogram signal display 17, or othersystems conventional in the art may also be integrated into the system10. It should be understood that embodiments consistent with the presentinvention may, and typically will, include other features not shown ordescribed herein in FIG. 1 for the sake of brevity and clarity. Forexample, an irrigated ablation catheter may typically include additionalelectrodes (and corresponding leads) and other features as known in theart.

The catheter 12 may include a cable connector portion or interface 18, ahandle 20 and a shaft 22 having a proximal end 24 and a distal end 26.Disposed on the shaft 22 near the distal end is an ablation tipelectrode 28 _(T). The system 10 may further include an electricalreturn which is used in cooperation with the ablation electrode 28 _(T),such as a skin patch 30 (i.e., an RF dispersive indifferentelectrode/patch).

The shaft 22 may further include one or more other electrodes,configured for intra-cardiac use, such as various ring electrodes 28_(R). It should be re-iterated that the catheter 12 may include stillother electrodes, and that in any event, in other embodiments, one ormore such other electrodes may be used for any number of diagnosticand/or therapeutic purposes. For instance, such electrodes and thereforesuch catheters may be used for performing ablation procedures as noted,but also for cardiac mapping, electrophysiological (EP) studies andother like procedures.

The general structural and functional features of catheter systems suchas those generally comprising the catheter 12, the fluid source 14 andthe RF ablation generator 16 are generally well known to those of skillin the art. For example, the fluid source 14 can comprise various knownassembly, including fixed volume rolling pumps, variable volume syringepumps and other pump assembly known to those skill in the art, includinga gravity fed supply as shown. The fluid provided by fluid source 14 maycomprise a suitable biocompatible fluid, such as saline. The RF ablationgenerator 16 may comprise conventional apparatus, such as a commerciallyavailable unit sold under the model number IBI-1500T RF Cardiac AblationGenerator, available from Irvine Biomedical, Inc. Of course, the RFablation generator 16 can also comprise other known energy sources.

FIG. 2 is a cross-sectional view of a conventional distal electrodeassembly 32 commonly used in an irrigated ablation electrode design. Theassembly 32 includes a manifold 34 and an ablation electrode 36 whichextend together along a center (longitudinal) axis 38. The manifold 34includes a proximal coupling portion 40 that is configured forconnection to the shaft 22. The manifold 34 further includes acentrally-disposed distribution cavity that features an inlet and isadapted for connection to an irrigation fluid delivery tube 42. Themanifold 34 also includes a plurality of proximal irrigation passagewaysor ports 44 (“ports”) extending from the distribution cavity to theouter surface of the manifold 34. The manifold 34 also includes a distalcoupling portion configured in size and shape to mate with acorresponding blind bore 46 formed in the ablation electrode 36. Asconventional, a generally straight irrigation passageway 48 is formedthrough the electrode 36, extending along the center axis 38.Accordingly, a thermal sensor, such as a thermocouple 50 or the like,must be offset significantly from the center axis 38. As described inthe Background, this off-center positioning of the sensor can lead toinconsistent temperature measurements, particularly in a parallelcontact orientation, depending on which side of the electrode 36 iscontacting the tissue (i.e., note, that the sensor 50 is much closer tothe “top” side of the electrode and will thus be more sensitive totemperature levels/changes on that side and less sensitive totemperature levels/changes on the other side).

It is desirable to position the thermal sensor on the center axis, at ornear the center axial location in the electrode. In order to do so, thedistal irrigation passageway, in accordance with the invention, is movedaway from its conventional on-axis position to an off-center position.FIG. 3A-FIG. 6 illustrate various embodiments of the invention; however,common to all the embodiments is the inclusion of (i) one or more distalirrigation passageway(s) with respective openings that are offset indistance from the center axis with (ii) an on-center (or near on-center)located temperature sensor.

FIG. 3A is a cross-sectional view of a first embodiment of a distalelectrode assembly 52. The assembly 52 includes a manifold 54 affixed toan ablation electrode 56. Together, the assembly 52 extends along acenter (longitudinal) axis 58. The manifold 54 may be generallycylindrical in shape, at least as to its radially-outermost surface.Moreover, many embodiments of electrode 56 are also generallycylindrical in shape, terminating in a hemispherical distal end. Thecylindrical shape of the manifold 54 and of the electrode 56 may besubstantially similar to one another and generally have the same overalldiameter, which can provide or create a flush or substantially smoothouter body or profile for electrode assembly 52. Significantly, asalluded to a defining feature of the assembly 52 is that it includes anoff-center distal irrigation passageway 60 with an opening 62 at adistal tip 64 of the electrode 56 where the opening is offset indistance from the center axis. In the first embodiment, the distalirrigation passageway 60 is straight and is substantially parallel tothe center axis 58, and whose opening 62 is offset in distance by afirst amount 66 from the axis 58. The assembly 52 further includes athermal or temperature sensor 68, which is illustrated as being locatednear center, being offset in distance from the center axis 58 by asecond amount 70. Note, that the first offset amount 66 need not begreater than the second offset amount 70. It is sufficient that thetemperature sensor 68 is closer to the center axis than would otherwisebe as per conventional designs using on-axis distal irrigationpassageways. Through the foregoing, the temperature sensor 68 can belocated closer to the center axis 58 and closer to the axial center ofthe electrode 56 than that provided for under conventional designs.

FIG. 3B is an axial head-on view showing more clearly the off-centerlocation of the irrigation passageway 60, more particularly the offsetin distance of the distal opening 62 from the center axis.

Referring now to FIGS. 3A-3B, the manifold 54 is further configured toprovide a plurality of cavities and/or passageways adapted to facilitatethe flow of irrigation fluid therethrough to the manifold's outersurface (proximal irrigation) as well as to the electrode 56 fordelivery by the distal irrigation passageways (distal irrigation). Themanifold 54 is formed of a main body 72, and includes a proximalcoupling portion 74 and a distal coupling portion 76. The proximalcoupling portion 74 is configured in size and shape to be connected tothe distal end 26 of the shaft 22. In the illustrated embodiment, theproximal coupling portion 74 is cylindrical. Likewise, the distalcoupling portion 76 is configured in size and shape to be receivedwithin a blind bore 78 of the ablation electrode 56 for attachmentthereto. The electrode 56 may be connected by various known mechanisms,including adhesives, press-fit configurations, snap-fit configurations,threaded configurations, or various other mechanism known to persons ofordinary skill in the art.

The manifold 54 further includes a centrally-disposed distributioncavity 80, configured for transporting and/or distributing fluidthroughout various portions of the electrode assembly 32. The cavity 80has an inlet 82, which is configured to cooperate with a fluid deliverytube 84. In particular, the fluid delivery tube 84 may be securelyprovided in fluid communications with the distribution cavity 80 throughthe insertion of the tube 84 in the inlet 82. An optional seal (notshown) may be provided about (around) the tube 84 after insertionthereof into the inlet 82. The fluid delivery tube 84 may be disposed ina central lumen 86 of the shaft 22, as shown.

The manifold 54 may further include one or more proximal irrigationpassageways or ports 88 (hereinafter “ports” 88) extending (e.g., at anacute angle) between the distribution cavity 80 to an outer surface ofthe manifold 54. The distribution cavity 80 may serve to distributeirrigation fluid to the proximal ports 88. In one embodiment, themanifold 54 may be formed so that a plurality of proximal ports 88 aresubstantially equally distributed around the circumference of themanifold to provide substantially equal distribution of fluid. It shouldbe understood that the art is replete with various configurations anddesign approaches for proximal irrigation passageways, and willtherefore not be further elaborated upon.

The manifold 54 also includes a tapered lumen portion 94, locatedintermediate the main, irrigation distribution cavity 80 and the distalirrigation passageway 60, configured to transition the fluid paths froman on-center path (i.e., the cavity 80) to an off-center path (i.e., thedistal irrigation passageway 60).

The manifold 54 may also include guideways (not shown) configured toallow one or more electrical connection wires to pass therethrough. Forexample, a main ablation power wire 90 is shown in FIG. 3A, which isconnected at the proximal end to the RF ablation generator 16 (bestshown in FIG. 1), is routed through lumen 86 (or other lumen providedwithin shaft 22), passes through the manifold 54 through such a guidewayand is then electrically terminated at the ablation electrode 56.Likewise, a temperature sensor connection wire 92 may also follow asimilar path as the power wire 90, and is then electrically terminatedat the sensor 68.

The manifold 54 may also comprise thermally nonconductive or reduced(i.e. poor) thermally conductive material that serves to insulate thefluid from the remaining portions of electrode assembly 52, for example,the electrode 56. Moreover, such selected material(s) for the manifold54 may also exhibit electrically nonconductive properties.Comparatively, the manifold 54 may have lower thermal conductivity thanthe electrode 56. In one embodiment, the manifold 54 may comprise areduced thermally conductive polymer material. A reduced thermallyconductive material is one with physical attributes that decrease heattransfer by about 10% or more, provided that the remaining structuralcomponents are selected with the appropriate characteristics andsensitivities to maintain adequate monitoring and control of theprocess. Moreover, a reduced thermally conductive material may includepolyether ether ketone (“PEEK”). Further examples of reduced thermallyconductive materials that may be useful in conjunction with the presentinvention include, but are not limited to, high-density polytheylene,polyimides, polyaryletherketones, polyetheretherketones, polyurethane,polypropylene, oriented polypropylene, polyethylene, crystallizedpolyethylene terephthalate, polyethylene terephthalate, polyester,polyetherimide, acetyl, ceramics, and various combinations thereof.Moreover, for some embodiments, the manifold 54 may be substantiallyless thermally conductive than the electrode 56. As a result, theirrigation fluid flowing through manifold 54 may have very littlethermal effect on the electrode 56 due to the poor thermal conductivityof manifold 54 (e.g. less than 5% effect), and preferably may havenearly 0% effect.

The ablation electrode 56 is configured to have an ablation surface,including distal tip 64. The electrode 56 may generally compriseelectrically and potentially thermally, conductive materials, as knownto those of ordinary skill in the art. Examples of suitable electricallyconductive materials include (but are not limited to) gold, platinum,iridium, palladium, stainless steel, and various mixtures, alloys andcombinations thereof. In one embodiment, the distal tip 64 may berounded (e.g., partially spherical or hemispherical), although otherconfigurations may be used.

The electrode 56 is further configured with a sensor cavity 96 that isconfigured in size and shape to receive the temperature sensor 68. Inthe illustrated embodiment, the sensor 68 may be disposed near thecentral longitudinal axis 58. In alternate embodiments described inconnection with FIGS. 4A-4B, 5A-5B and 6, the sensor 68 may be locatedsubstantially on axis 58. Such improved positioning of the sensor 68 mayfurther enhance the temperature sensing properties or capabilities ofthe electrode assembly 52. The sensor 68 may comprise conventionalcomponents known in the art, including, for example, thermocouples orthermistors. The sensor 68 may further be substantially surrounded, orat least partially encapsulated, by a thermally conductive andelectrically non-conductive material. This thermally conductive andelectrically non-conductive material can serve to hold temperaturesensor 68 in place within the electrode 56 and provide improved heatexchange between the sensor 68 and the electrode 56. Such material maycomprise, for example, thermally conductive resins, epoxies, or pottingcompounds.

The electrode 56 further includes the off-center distal irrigationpassageway 60 having the opening 62 that is offset in distance from thecenter axis, described above. The interior of the passageway 60 may be,and preferably is, thermally insulated from the electrode body, forexample, through the use of thermally insulated tubular element 98. Thisinsulation is to minimize temperature disturbances to the sensedelectrode temperature that may be introduced by the irrigation fluidlowering the temperature of the electrode body.

Thermally insulated tubular element 98 may comprise thermallynon-conductive and/or poor conductive material. Such material mayinclude, but is not limited to, high-density polyethylene, polyimides,polyaryletherketones, polyetheretherketones, polyurethane,polypropylene, oriented polypropylene, polyethylene, crystallizedpolyethylene terephthalate, polyethylene terephthalate, polyester,polyetherimide, acetyl, ceramics, and various combinations thereof.

FIGS. 4A-4B illustrate a second embodiment of the inventive distalelectrode assembly, which is referred to in the drawings as assembly52′. The assembly 52′ is similar to the assembly 52, and thus only thedifferences will be described. The assembly 52′ extends the principle ofan off-center irrigation passageway with an opening that is offset indistance from the center axis to a dual passageway embodiment, and whichfurther uses an on-center temperature sensor (in contrast to the nearcenter location for the thermal sensor in the embodiment of FIGS.3A-3B). The distal irrigation passageways include a first irrigationpassageway 60′₁ and a second irrigation passageway 60′₂. Each one of thepassageways 60′₁, 60′₂ are offset from the center axis 58. As shown inFIG. 4A, each passageway 60′₁, 60′₂ is generally straight, extendingalong its own longitudinal axis, which longitudinal axis intersects andforms an acute angle θ with respect to the center axis 58. The acuteangle θ may assume a wide range of values, adequate to vacate the spaceon (or near) the center axis 58 so as to allow the temperature sensor 68to be mounted therein. In the illustrated embodiment, the angle θ isabout 15° (degrees), although it should be appreciated that variationsfrom this angle are possible and still achieve the purpose of vacatingthe space in and around the center axis 58.

As shown in FIG. 4B, the distal openings of the irrigation passageways60′₁, 60′₂ are also offset in distance from the center axis 58 by arespective offset amount (distance) designated 66′. Although notrequired, in the illustrated embodiment, both passageways 60′₁, 60′₂(and openings thereof) are offset in the same manner (i.e., the sameacute angle θ and the same offset distance 66′ from the center axis 58),making the illustrated embodiment symmetrical. Further variations arepossible. For example, a three distal irrigation passageway embodimentis contemplated where the three passageways are equally distributedaround the distal tip of the ablation electrode (i.e., the first, secondand third offset amounts (distances) of the respective openings from thecenter axis may be the same and the circumferential spacing of thepassageways may be the same).

Referring to FIGS. 4A-4B, the assembly 52′ includes a manifold 54′ andan ablation electrode 56′, which are similar to the manifold 54 andelectrode 56 described above. Again, only the differences will bedescribed. The manifold 54′, rather than having a tapered lumen portion94, includes a pair of feed lumens 100 formed in the main body thatextend away from the distribution cavity 80′ towards the passageways atsubstantially the same angle θ at which the passageways 60′₁, 60′₂ areoriented. The passageways 60′₁, 60′₂ and the lumens 100 are thusconfigured such that when the manifold 54′ and the electrode 56′ areassembled, the passageways are in alignment with a respective one of thelumens 100. This completes a fluid path from the distribution cavity 80′to the distal openings 62′ of the passageways 60′₁, 60′₂. In addition,the distal coupling portion 76′ of the manifold 54′ is modified toaccommodate the presence of the feed lumens 100, while the receivingbore 78′ of the electrode 56′ is also modified in a like andcomplementary way to cooperate with the modified distal coupling portion76′. Preferably, each passageway 60′₁, 60′₂ is thermally insulated,again, such as through the use of thermally insulated tubular elements98′ of a suitable size and length.

The electrode 56′ includes a sensor cavity 96′ located substantially onthe center axis 58, which in turn allows for the temperature sensor 68to be disposed substantially on the center axis 58 as well, providingimproved temperature monitoring as described above.

FIGS. 5A-5B illustrate a third embodiment of the inventive distalelectrode assembly, which is referred to in the drawings as assembly52″. The assembly 52″ is similar to assemblies 52 and 52′, and thus onlythe differences will be described. The assembly 52″ likewise embodiesthe principle of off-center distal irrigation passageways havingrespective openings that are offset in distance from the center axiscombined with an on-center temperature sensor. The distal irrigationpassageways include a first irrigation passageway 60″₁ and a secondirrigation passageway 60″₂ having respective distal openings 62″₁, 62″₂.(FIG. 5B) that are offset in distance from the center axis. The firstand second passageways 60″₁, 60″₂ are also offset from the center axis58. As shown in FIG. 5A, each passageway 60″₁, 60″₂ has a respective,generally straight first portion 102, which extends along its ownlongitudinal axis, which longitudinal axis forms an acute angle θ′ withaxis 58. Each passageway 60″₁, 60″₂ further includes a respective,generally straight second portion 104, which extends along its ownlongitudinal axis that is generally parallel to the center axis 58.Finally, each passageway 60″₁, 60″₂ includes a respective, generallycurved portion 106 that is intermediate the first and second straightportions 102, 104. As described, the axis associated with portion 102intersects with and forms an acute angle θ′ with axis 58. The angle θ′may assume a wide range of values selected so that the placement of thepassageways vacates the space on (or near) the center axis 58 so as toallow the temperature sensor 68 to be mounted within the electrode 56″on the center axis 58. In the illustrated embodiment, the acute angle θ′is about 30° (degrees), although it should be appreciated thatvariations from this angle are possible and still achieve the purpose ofvacating the space within the electrode 56″ on the center axis 58.

As shown in FIG. 5B, the distal openings 62″₁, 62″₂ of the irrigationpassageways 60″₁, 60″₂ are offset in distance from the center axis 58 byan offset amount (distance) designated 66″. Although not required, inthe illustrated embodiment, both passageways 60″₁, 60″₂ and openingsthereof 62″₁, 62″₂ are offset in the same manner (i.e., the same acuteangle θ′ and the same offset distance 66″ from the center axis 58),making the illustrated embodiment symmetrical.

Referring to FIGS. 5A-5B, the assembly 52″ includes a manifold 54″ andan ablation electrode 56″ that are similar to the manifold 54′ andelectrode 56′ described above. Again, only the differences will bedescribed. The distribution cavity 80″ formed in the manifold bodyextends therethrough on-axis (i.e., similar to a through-bore). Thedistal coupling portion 76″ is modified in view of the change to thedistribution cavity 80″, while the blind bore 78″ of the electrode 56″is also modified in a like and complementary way to cooperate with themodified coupling portion 76″. The passageways 60″₁, 60″₂ are preferablythermally insulated, such as through the use of thermally insulatedtubular elements 98″ of a suitable size and length. The distal end ofthe distribution cavity 80″ (i.e., the distal opening of distributioncavity 80″) is sized so as to accommodate a pair of such tubularelements 98″, in a tight fit relation or in other ways known in the artto effect a secure attachment. The manifold 54″ may also include amechanical feature 94″ (e.g., a stop or the like) that impedes anyfurther axial insertion of the tubular elements 98″ into thedistribution cavity of the manifold once the terminal ends of thetubular elements 98″ reach the stop. Once assembled, the tubularelements 98″ provide a pair of distal irrigation passageways extendingfrom the distribution cavity 80″ to the distal openings on the electrodetip.

The electrode 56″ also includes a sensor cavity 96″ locatedsubstantially on the center axis 58, which in turn allows for thetemperature sensor 68 to also be disposed substantially on the centeraxis 56, providing the improved temperature monitoring as describedabove.

FIG. 6 is a perspective view of a distal end of a catheter incorporatingthe inventive electrode assembly 52″. As shown, the distal opening 62″₂of the irrigation passageway 60″₂ that is visible in the figure isoffset in distance from the center axis 58. As described and illustratedabove, the positioning allows for the temperature sensor 68 to becentrally disposed within the electrode 56″ on the center axis 58 (ornear the center axis in the embodiment of FIGS. 3A-3B).

A method of manufacturing an electrode assembly, in any of theembodiments as described above, is provided and involves a number ofsteps. First, providing an electrode portion of a distal electrodeassembly with a first irrigation passageway having a first opening at adistal tip surface thereof, where the first opening is offset indistance from the center axis of the electrode assembly. The step ofproviding the electrode may further include the substep of providing atemperature sensor on or near the center axis of the electrode assembly,in the space vacated by moving the irrigation passageway(s) tooff-center locations. The next step involves coupling the electrode to amanifold portion of the electrode assembly. Finally, the last stepinvolves coupling the free end of the manifold (i.e. proximal couplingportion of the manifold) to a catheter shaft.

Although numerous embodiments of this invention have been describedabove with a certain degree of particularity, those skilled in the artcould make numerous alterations to the disclosed embodiments withoutdeparting from the spirit or scope of this invention. All directionalreferences (e.g., plus, minus, upper, lower, upward, downward, left,right, leftward, rightward, top, bottom, above, below, vertical,horizontal, clockwise, and counterclockwise) are only used foridentification purposes to aid the reader's understanding of the presentinvention, and do not create limitations, particularly as to theposition, orientation, or use of the invention. Joinder references(e.g., attached, coupled, connected, and the like) are to be construedbroadly and may include intermediate members between a connection ofelements and relative movement between elements. As such, joinderreferences do not necessarily infer that two elements are directlyconnected and in fixed relation to each other. It is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative only and not limiting.Changes in detail or structure may be made without departing from thespirit of the invention as defined in the appended claims.

What is claimed is:
 1. A distal assembly of an irrigated ablationcatheter, comprising: a manifold and an ablation electrode extendingalong a central axis; a temperature sensor disposed in said electrodeconfigured to produce a temperature signal indicative of a temperaturevalue of said electrode; said manifold comprising a centrally-disposeddistribution cavity, wherein said manifold is configured for connectionto a distal end of a shaft of said catheter, and wherein the manifoldfurther comprises a reduced thermally conductive material configured toinsulate the temperature sensor and the ablation electrode from thecentrally-disposed distribution cavity; said ablation electrodeincluding a first irrigation passageway having a first opening at adistal tip of said electrode, said first opening being offset indistance from said central axis; wherein said first opening of saidfirst irrigation passageway is offset in distance from said central axisby a first amount of offset; wherein said temperature sensor and saidcentrally-disposed distribution cavity are substantially in line withsaid central axis, and wherein the thermal sensor and the ablationelectrode are configured to be thermally insulated from the firstirrigation passageway.
 2. The assembly of claim 1 wherein saidtemperature sensor comprises one of a thermocouple and a thermistor. 3.The assembly of claim 1 further including a thermally insulated tubularelement disposed in said first irrigation passageway.
 4. The assembly ofclaim 1 wherein said manifold includes a main body having thecentrally-disposed distribution cavity in communication with an inletfor connection to a supply of irrigation fluid, said manifold furtherincluding one or more proximal irrigation ports extending from saiddistribution cavity to an outer surface of said manifold, saiddistribution cavity and said one or more proximal irrigation ports beingarranged for fluid communication therebetween.
 5. The assembly of claim4 wherein said manifold further includes a tapered lumen portion betweensaid distribution cavity and said first irrigation passageway.
 6. Theassembly of claim 1 wherein said electrode further includes a secondirrigation passageway having a second opening on said distal tip of saidelectrode, said second opening being offset in distance from saidcentral axis by a second amount of offset.
 7. The assembly of claim 6wherein said second amount of offset is substantially equal to saidfirst amount of offset and wherein said first and second openings aresubstantially symmetrical with respect to said central axis.
 8. Theassembly of claim 6 wherein said electrode further includes a thirdirrigation passageway having a third opening on said distal tip of saidelectrode, said third irrigation passageway being offset in distancefrom said central axis by a third amount of offset.
 9. The assembly ofclaim 8 further including thermally insulated tubular elements disposedin at least one of said first, second and third irrigation passageways.10. The assembly of claim 9 wherein each of said irrigation passagewaysincludes a respective thermally insulated tubular element.
 11. Theassembly of claim 6 wherein said manifold includes a main body having aproximal coupling portion configured for connection to said cathetershaft and a distal coupling portion configured for connection to saidelectrode, said manifold having the centrally-disposed distributioncavity in communication with an inlet for connection to a supply ofirrigation fluid, said manifold further including a pair of feed lumensextending from said distribution cavity and configured for respectivealignment with said first and second irrigation passageways.
 12. Theassembly of claim 11 wherein said manifold includes a main body having aproximal coupling portion configured for connection to said cathetershaft and a distal coupling portion configured for connection to saidelectrode, said manifold having the centrally-disposed distributioncavity in communication with an inlet for connection to a supply ofirrigation fluid, said distribution cavity comprising a distal openingconfigured in size and shape to receive a pair of thermally insulatedtubular elements associated with the first and second irrigationpassageways.
 13. An irrigated ablation catheter, comprising a shafthaving a proximal end and a distal end; a manifold comprising acentrally-disposed distribution cavity, wherein said manifold isconfigured for connection to said distal end of said catheter shaft; anablation electrode wherein said manifold and said electrode extend alonga central axis, said electrode including a first irrigation passagewayhaving a first opening at a distal tip thereof that is offset indistance from said central axis; and a temperature sensor disposed insaid electrode configured to produce a temperature signal indicative ofa temperature value of said electrode, wherein the manifold furthercomprises a reduced thermally conductive material configured to insulatethe temperature sensor and the ablation electrode from thecentrally-disposed distribution cavity, and wherein said first openingis offset in distance from said central axis by a first amount ofoffset, wherein said temperature sensor and said centrally-disposeddistribution cavity are substantially in line with said central axis,wherein the temperature sensor and the ablation electrode are configuredto be thermally insulated from the first irrigation passageway.
 14. Thecatheter of claim 13 wherein said electrode further includes a secondirrigation passageway having a second opening on said distal tip of saidelectrode, said second irrigation passageway being offset in distancefrom said central axis by a second amount of offset.
 15. The catheter ofclaim 14 wherein said second amount of offset is substantially equal tosaid first amount of offset and wherein said first and second openingsare substantially symmetrical with respect to said central axis.
 16. Thecatheter of claim 14 wherein said electrode further includes a thirdirrigation passageway having a third opening on said distal tip of saidelectrode, said third irrigation passageway being offset in distancefrom said central axis by a third amount of offset.
 17. The catheter ofclaim 16 further including a thermally insulated tubular elementdisposed in at least one of said first, second, and third irrigationpassageways.